Numerous systems and methods have been disclosed to characterize and treat crude oils or refinery feedstocks that contain acids in several forms. The acids in the feedstocks may be organic acids such as carboxylic or naphthenic or mineral acids such as hydrochloric, phosphoric, hydrogen sulfide and various oxidized forms of hydrogen sulfide such as sulfuric acid. Naphthenic acid is a type of organic acid commonly present in acidic crudes. There are publications teaching the treatment and prevention of acid corrosion in petroleum feedstocks with the demineralization and alkali treatment of crude oil, the use of organic corrosion inhibitors, and selection of equipment and materials for handling petroleum feedstocks by alloying metals with anticorrosive additives, such as Cr, Mo, Ni, etc.
Evaluation of corrosivity of refinery feedstocks has typically been done by a classic model considering the Total Acid Number (TAN) of the feedstocks. The TAN number is computed based on milligrams of KOH required to neutralize one gram sample of the crude. If the feedstock has a TAN greater than 0.5, the crude is usually considered corrosive. One traditional approach has been blending high naphthenic acid crudes with low naphthenic acid crudes to a predetermined TAN number, e.g., below 0.5 for crudes or 1.5 for certain side-cuts, such as vacuum gas oil, or by avoiding refining crudes having relatively high quantities of naphthenic acids. U.S. Patent Application No. 2008/0164137 discloses that naphthenic acid corrosivity can be correlated with the chemical composition of naphthenic acids, especially with respect to the ratio between an alpha fraction and a beta fraction of the naphthenic acids
There is still a need for improved methods and systems to characterize refinery feedstocks by their corrosivity characteristics.